The role of the organic matrix in the mineralization of dentin is being determined. Principal attention is being given to the dentin phosphophoryn component. After isolation from rat incisor or bovine molars, the phosphophoryn component is purified chromatographically, then its physico-chemical properties, calcium binding interactions, and collagen interactions are being studied. Both in vivo and in vitro studies of the biosynthesis, secretion and cross-linking of the phosphophoryn are being carried out. Further studies of the role of dentin matrix components in bond induction systems are in progress.